A gradient plasticity creep model accounting for slip transfer/activation at interfaces evaluated for the intermetallic NiAl-9Mo

Abstract Interfaces can act as dislocation obstacles, sinks or dislocation sources and, therefore, influence strongly the mechanical properties of metals. To consider these effects at high temperature creep, a three-dimensional gradient crystal plasticity model is introduced. The interaction between dislocations and the fiber-matrix interface is included by an interface flow rule, which accounts for the gradient stresses and the normal component of the Cauchy stress on the interface. Motivated by the interface-enriched generalized finite element method (IGFEM), continuous shape functions allowing for weak discontinuities are introduced. These shape functions are used to evaluate the interface flow rule at sharp interfaces and are validated by comparing numerical simulation results of a laminate for single slip with an analytical solution. To investigate the slip transfer/activation at the interface, the directionally solidified NiAl-9Mo composite is modeled as regular fibrous microstructure. The simulated creep curves agree well with experimentally measured ones. It is found that the stress dependency of the interface flow rule is necessary to reproduce the well known composite's Norton behavior. The simulations reveal that the creep behavior of the composite is mainly controlled by the fibers and the interface properties. Finally, the specific shape of the creep curve could be explained.